Without limiting the scope of the invention, its background is described in connection with additive compounds that act as multifunctional materials, as an example.
Contamination of materials by microorganisms such as pathogenic bacteria, molds, fungi and viruses is of great concern in the medical industry, the food and restaurant industries, as well as in consumer products as a result of the potential for the spread of infections. Survival of microorganisms on various materials and transfer of these microorganisms between materials, animals and humans has been demonstrated, and it is widely accepted that microorganism-contaminated materials can be elements in cross-infections and transmission of diseases caused by microorganisms. Furthermore, the structure and characteristics of biofilms allow the growth and proliferation of contaminants and make the cleaning and removal of pathogenic bacteria, molds, fungi and viruses extremely difficult.
Microorganisms have strong abilities to survive on ordinary materials and can stay alive for as long as 90 days. These microorganisms can further develop into firmly attached biofilms. A biofilm is an accumulation of microorganisms (e.g., bacteria, fungi, and/or protozoa, with associated bacteriophages and other viruses) embedded in a polysaccharide matrix and adherent to solid biologic or non-biologic surface.
Biofilms are remarkably difficult to treat with antimicrobials, which may be readily inactivated or fail to penetrate into the biofilm. In addition, microorganisms within biofilms have increased (e.g., up to 1000-fold higher) resistance to antimicrobial compounds, even though these same microorganisms are sensitive to these agents if grown under planktonic conditions. Furthermore, microorganisms express new, and sometimes more virulent phenotypes when grown within a biofilm. Such phenotypes may not have been detected in the past because the organisms were grown on rich nutrient media under planktonic conditions. The growth conditions are quite different particularly in the depths of biofilms, where nutrients and oxygen are usually limited, and waste products from neighbors can be toxic. In short, microorganisms found at the bottom of the biofilm look and act different from microorganisms located at the surface.
Biofilms represent a serious problem in environmental, medical and industrial fields. Additionally, biofilms increase the opportunity for gene transfer between/among microorganisms allowing microorganisms resistant to antimicrobials or chemical biocides to transfer the genes for resistance to neighboring susceptible microorganisms. Gene transfer can convert a previous avirulent commensal organism into a highly virulent pathogen. Certain species of microorganisms communicate with each other within the biofilm. As their density increases, the organisms secrete low molecular weight molecules that signal when the population has reached a critical threshold, e.g., quorum sensing, is responsible for the expression of virulence factors.
Microorganisms embedded within biofilms are resistant to both immunological and non-specific defense mechanisms of the body. Contact with a solid surface triggers the expression of a panel of bacterial enzymes, which catalyze the formation of sticky polysaccharides that promote colonization and protection. The structure of biofilms is such that immune responses may be directed only at those antigens found on the outer surface of the biofilm, and antibodies and other serum or salivary proteins often fail to penetrate into the biofilm. In addition, phagocytes are unable to effectively engulf a bacterium growing within a complex polysaccharide matrix attached to a solid surface. This causes the phagocyte to release large amounts of pro-inflammatory enzymes and cytokines, leading to inflammation and destruction of nearby tissues. Because biofilm formation is triggered by the survival and adherence of microbes onto different materials, the introduction of biocidal functions into the target materials can be an effective method to inactivate the microbes and thus control biofilms.
In addition to the medical and healthcare fields, the food and restaurant industries, as well as in consumer are increasingly concerned with microbial contamination, e.g., food contact between contaminated articles. Multiple outbreaks of food borne bacterium such as E. coli, have made people increasingly conscious of methods to control the spread of such bacterium. Food contact materials such as cutting boards, sponges, towels and the like have long been suspected to be vectors for the spread of food borne microorganisms. Therefore, the induction of biocidal properties should be an effective feature of healthcare and hygienic-use applications.
The foregoing problems have been recognized for many years and while numerous solutions have been proposed, none of them adequately address all of the problems in a single device, e.g., effectiveness against many forms of bacteria, toxicity, stability and rechargeability.